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PubMed1994

Sound localization in hemispherectomized patients.

In order to precisely evaluate the consequences of cortical damage on free-field sound localization in humans, the present study examined response accuracy to auditory targets in three hemispherectomized patients and IQ-matched controls. Listeners reported sound location by pointing with their dominant hand to the apparent sound location in an anechoic chamber. Two conditions were tested: (i) localization of a fixed-sound source and (ii) localization of the beginning and the end of a simulated moving stimulus. In both conditions, the responses of the patients were less accurate than those of the controls in the hemifield contralateral to their removed hemisphere. Moreover, the single-case analyses revealed that the performances obtained with fixed sources were generally more precise than those obtained with moving sources. This result is discussed in terms of a differential involvement of cortical and subcortical pathways in the processing of stationary and moving sounds. Finally, the age at surgery and the post-surgical interval were related with the magnitude of the deficits, suggesting the possible influences of functional reorganization and cerebral plasticity.

Adolescent↗
PubMed1992

The syndrome of absent or faint second heart sound, rapid systole and forward collapsing pulse.

A syndrome consisting of an absent or faint second heart sound, prominent cardiac impulse and non-regurgitant or forward collapse of the pulse is described. There was, moreover, no second sound or flow murmur audible in either the aortic or the pulmonary area even though the impulse and collapsing pulse suggested a hyperdynamic circulation; the upstroke was sharp but without the full waterhammer knock. It is argued that the dominant cause of the collapsing pulse will usually be vasodilation, that absence or faintness of the second sound is due to a narrow angle of divergence between the ventricular and arterial pressure decay curves, and that in marked contrast to aortic regurgitation the quality of the impulse derives from rapid systole of lightly loaded ventricles. Although they described its separate elements, pre-homeostatic era clinicians may have overlooked the syndrome in the belief that the heart regulated a largely passive circulation, regarding only primary intracardiac events and the first heart sound as important. Sir William Stokes nevertheless foresaw that alterations in the second sound might be due to changes in vascular tone as well as in elasticity. Wider recognition, deeper understanding and appropriate correction of this syndrome may prove both useful and enlightening.

Adult↗
PubMed1986

Memory formation in birds: 1. Avoidance conditioning of the budgerigar (Melopsittacus undulatus) to sound stimuli.

A system is described for avoidance conditioning of the budgerigar (Melopsittacus undulatus), for sound patterns consisting of one or two sequential subunits and to discriminate between two closely resembling sounds. Electric shock was used as the unconditioned stimulus. Simple conditioning was accomplished in about 300-400 trials. After a given sound pattern was firmly fixed by conditioning, discrimination between this and a new sound pattern was established relatively rapidly by using several consecutive sessions in which the two patterns were mixed. Discrimination was reinforced by associating the two signals by opposing electric shocks. An overnight rest period after the first few sessions improved the rate of conditioning during the following experimental period. A temporary, partial or complete extinction of conditioning was produced by longer rest intervals, but the original conditioning was reestablished by subjecting the animal to a few trials of reconditioning. Short intercalations of a new conditioned stimulus had no effect on the retention of the original conditioning whereas a random mixing of the first conditioned stimulus with a second produced a temporary decay in the original conditioning. The experimental system described here is useful for studying physiological and biochemical changes accompanying a memory process based on a linear sequence of sound patterns.

Animals↗
PubMed1992

Hearing and sound localization in blind mole rats (Spalax ehrenbergi).

Two blind mole rats were tested for their ability to detect and localize sound. The results indicate that blind mole rats have severely limited, and probably degenerate, auditory abilities. Although their 60-dB low-frequency hearing limit of 54 Hz is within the range for other rodents, the highest frequency they can hear at a level of 60 dB SPL is only 5.9 kHz, giving them the poorest high-frequency sensitivity yet observed in any mammal. In addition they have poor sensitivity as indicated by the fact that their lowest threshold is only 32 dB SPL (at 1 kHz). Finally, they are unable to localize brief sounds but retain a rudimentary ability to localize sounds of 0.5 s or longer. These results, combined with those of previous studies of subterranean species (i.e., blind mole rats, naked mole rats, and pocket gophers), suggest that poor auditory sensitivity, the loss of high-frequency hearing, and an inability to localize brief sounds is a degenerate state which may be characteristic of subterranean mammals. Thus it appears that an exclusive adaptation to a subterranean lifestyle (where airborne sound propagates poorly and where directional responses are limited by the tunnels) can result in vestigial auditory abilities just as the absence of light results in vestigial vision.

Acoustic Stimulation↗
PubMed1989

The relationship between temporomandibular joint sounds and malocclusion.

The relationship between temporomandibular joint (TMJ) sounds and the occlusion was evaluated in a sample of 226 patients before commencement of orthodontic treatment. TMJ sounds were recorded on videotape, using an audiovisual system, for subsequent classification into various categories. The prevalence of joint sounds was 36.3% (N = 82) of which 50% (N = 41) were categorized as reciprocal clicks. The occlusion (static and functional) and skeletal relationships generally did not appear to be significant factors in contributing to TMJ sounds in patients with malocclusions. However, a larger interincisal angle in the sound-present group, and dental wear and increased overbite in the reciprocal-clicking subgroup may be associated factors.

Adolescent↗
PubMed2005

Speech-sound duration processing in a second language is specific to phonetic categories.

The mismatch negativity (MMN) component of the auditory event-related potential was used to determine the effect of native language, Russian, on the processing of speech-sound duration in a second language, Finnish, that uses duration as a cue for phonological distinction. The native-language effect was compared with Finnish vowels that either can or cannot be categorized using the Russian phonological system. The results showed that the duration-change MMN for the Finnish sounds that could be categorized through Russian was reduced in comparison with that for the Finnish sounds having no Russian equivalent. In the Finnish sounds that can be mapped through the Russian phonological system, the facilitation of the duration processing may be inhibited by the native Russian language. However, for the sounds that have no Russian equivalent, new vowel categories independent of the native Russian language have apparently been established, enabling a native-like duration processing of Finnish.

Child↗
PubMed2006

Effects of spatial separation and stimulus probability on the event-related potentials elicited by occasional changes in sound location.

The ability to extract information about the spatial location of sounds plays an important role in auditory scene analysis. The present study examined the effects of spatial separation and stimulus probability on auditory event-related potentials (ERPs) to changes in sound location. In Experiment 1, we found that difference waves between ERPs elicited by standard and deviant stimuli showed a biphasic negative-positive response peaking around 126 and 226 ms after deviant onset. The amplitude of both responses increased with decreasing deviant stimulus probability, and increasing stimulus deviance. When the same stimuli were presented with equal probability for all locations (Experiment 2), there were no significant differences in the ERP amplitude and latency. These results suggest that the data reported in Experiment 1 are the result of contextual changes, rather than changes in simple acoustic features. Brain electrical source analyses are consistent with generators located in auditory cortices posterior to Heschel's gyrus. Although occasional changes in sound location elicit earlier peaks than the mismatch negativity (MMN) response reported for other types of deviation, their topographical distribution and behavior are consistent with MMN. The early latency of MMN for changes in sound location is interpreted in the context of an early-warning system to alert the organism to new sound sources in the environment.

Acoustic Stimulation↗
PubMed2001

Further studies on the activation of rat median raphe serotonergic neurons by inescapable sound stress.

Previous studies, using a biochemical measure of serotonergic neuronal function, show that inescapable, randomly presented sound pulses activate serotonergic neurons in the rat median raphe but not dorsal raphe nucleus. The present study reveals that this activation also occurs in serotonin projection areas, in hippocampus, nucleus accumbens and cortex but not in caudate nucleus. The selectivity of this response is examined by comparing the response to sound stress with that produced by morphine, a treatment known to selectively activate dorsal raphe but not median raphe serotonergic neurons. Two approaches are used in Sprague-Dawley rat to measure the activation of serotonergic neurons: (1) determination ex vivo of accumulation of 5-hydroxytryptophan (5-HTP) in tissue from the dorsal and median raphe nuclei, hippocampus, cortex, caudate nucleus, and nucleus accumbens following in vivo inhibition of aromatic amino acid decarboxylase; and (2) measurement of extracellular serotonin levels in hippocampus, caudate nucleus, and nucleus accumbens. Sound stress increases 5-HTP accumulation in median raphe nucleus, hippocampus, cortex, and nucleus accumbens, but not dorsal raphe nucleus or caudate nucleus. Sound stress also enhances extracellular serotonin levels in hippocampus and nucleus accumbens, but not caudate nucleus. In contrast, the morphine treatment enhances 5-HTP accumulation in dorsal raphe nucleus, cortex and caudate nucleus, but not in median raphe nucleus, hippocampus or nucleus accumbens. Furthermore, it increases extracellular serotonin levels in only the caudate nucleus. The combined effects of sound stress and morphine on 5-HTP accumulation are identical to those obtained by each treatment individually. These findings provide further support for the presence of serotonergic neurons within the median raphe nucleus that have a unique response profile. These neurons may have an important role in responses or adaptations to stress.

Adaptation, Physiological↗
PubMed2004

A high resolution computer model for sound propagation in the human thorax based on the Visible Human data set.

A parallel supercomputer model based on realistic tissue data is developed for sound propagation in the human thorax and the sound propagation behavior is analyzed under various conditions using artificial sound sources. The model uses the Visible Human male data set for a realistic representation of the human thorax. The results were analyzed in time and frequency domains. The analysis suggests that lower frequencies of around 100 Hz are more effectively transmitted through the thorax and that the spatial confinement of sound waves within the thorax results in a resonance effect at around 1500 Hz. The results confirm previous studies that show the size of the thorax plays a significant role in the type of sound generated at the chest wall.

Acoustics↗
PubMed2004

Neural classification of lung sounds using wavelet coefficients.

Electronic auscultation is an efficient technique to evaluate the condition of respiratory system using lung sounds. As lung sound signals are non-stationary, the conventional method of frequency analysis is not highly successful in diagnostic classification. This paper deals with a novel method of analysis of lung sound signals using wavelet transform, and classification using artificial neural network (ANN). Lung sound signals were decomposed into the frequency subbands using wavelet transform and a set of statistical features was extracted from the subbands to represent the distribution of wavelet coefficients. An ANN based system, trained using the resilient back propagation algorithm, was implemented to classify the lung sounds to one of the six categories: normal, wheeze, crackle, squawk, stridor, or rhonchus.

Algorithms↗
PubMed1996

An extended replication study of dental factors associated with temporomandibular joint sounds.

A previous study demonstrated associations between dental factors and joint sounds. To support these findings, this replication study was carried out in another sample of nonpatients. It was found that temporomandibular joint sounds are common in nonpatients. Their prevalence in young adults exceeded the prevalence in adults. The small size of the control group rendered the results of multivariate analysis statistically inconclusive. Tentative interpretation suggests that attrition of the anterior teeth or generally in the dentition, unilateral non-working-side interferences, morphologic occlusion, and premolar contacts are related to the presence of sounds. Temporomandibular joint sounds in nonpatients are considered to be normal and not a manifestation of subclinical problems. Definite answers on the causality of temporomandibular joint sounds will have to be based on prospective longitudinal studies.

Adolescent↗
PubMed2003

Sound velocity determination in gel-based emulsions.

Sound velocity is a main parameter in non destructive characterization, closely related to the elastic properties and to the microstructure of heterogeneous materials. The accurate determination of the sound velocity using pulse-echo technique relies on the ability to reduce pulse distortion and to measure specimen dimensions with a high precision. In the field of bio-mimetic materials and biological tissues, the nature of the specimen makes this last requirement highly difficult or inappropriate. The present work, using a through-transmission configuration, allows, in a stress free environment, to access the sound velocity in soft, low acoustic contrast materials without requiring the specimen dimensions. The specimen sound velocity is obtained from the echo time-of-flights through a Z-scan process providing the absolute medium sound velocity as reference. The technique uses an excitation burst at a frequency below the transducer resonance to ensure a significantly reduction in pulse distortions and improve signal-to-noise ratio. The accurate determination of the echo time-of-flight relies on a highly efficient cross-correlation/Hilbert transform signal processing. The method has been applied to gel-based emulsions of different microstructures considered as biomimetic phantoms, as well as to their constituents: pure gelatin and vegetable oil.

Biomimetic Materials↗
PubMed1997

Muscle sounds in Parkinson's disease.

BACKGROUND: A sound with a frequency of around 40 Hz can be heard, with a stethoscope, in the muscles of the hand and forearm during tonic contraction or movement. This sound is the acoustic correlate of the Piper rhythm seen in electromyographic records of muscle activity. The way in which motor activity is organised at the cortical level may determine the frequency of the sound heard. METHODS: The wrist extensor muscles in the forearm of seven patients with idiopathic Parkinson's disease, studied with and without antiparkinsonian treatment, and a control group of seven healthy men were auscultated during very strong extension of the wrist and during repeated slow flexion and extension of this joint. FINDINGS: In healthy people, the Piper-band sound made by muscle activity is 40-50 Hz. In all seven parkinsonian patients, when off medication, the normal Piper-band sound was replaced by a pulsatile muscle activity of 10 Hz during strong wrist extension, and in four patients during repeated flexion and extension of the wrist. After treatment with dopaminergic drugs, the Piper mode of muscle discharge was restored and motor performance was improved. INTERPRETATION: The Piper mode of muscle discharge is dependent on the normal functioning of pallidal projections to the motor areas of the cortex. In abnormal function a muscle discharge of 10 Hz dominates, which is suboptimal when fast or powerful contractions are necessary.

Adult↗
PubMedDate not supplied

The spatial attributes of stimulus frequency in the median sagittal plane and their role in sound localization.

Stimulus cues used to locate sounds in the median sagittal plane were investigated. Listeners first were required to report the location of noise bands 1.0 kHz wide whose center frequencies ranged from 4.0 through 14.0 kHz. It was found that the apparent locations of the stimuli depended on their frequency compositions, not their places of origin. As the center frequency was increased from 4.0 to about 12.0 kHz, the apparent location of the sound moved from in front of the subject to the rear. Then, at center frequencies of around 13.0 kHz, the sounds again appeared to come from the front. The authors infer that different frequency regions within the sound's spectrum possess specific spatial referents along the median sagittal plane. When the bandwidth was increased to 4.0 kHz, listeners could locate the stimuli with reasonable proficiency only for the sectors of the median sagittal plane that were represented by the spatial referents inherent in the frequency composition of the stimulus. Finally, a stimulus comprising all audible frequencies above 4.0 kHz could be located proficiently, and it is concluded that this sound, unlike the others, contained all spatial referents for the median sagittal plane, hence the superior performance on the localization task.

Acoustic Stimulation↗
PubMedDate not supplied

Temporary hearing loss induced by combinations of intense sounds and nonsteroidal anti-inflammatory drugs.

Intense sounds were delivered to 11 subjects with normal hearing both before and during administration of standard doses of four nonsteroidal anti-inflammatory drugs. After four days of aspirin treatment (3.9 g daily), the subjects' resting hearing levels raised by about 10 dB. Administration of intense sounds that had previously been shown to produce about 12 dB of temporary hearing loss added increments of 10 to 15 dB to the aspirin-induced hearing loss. That is, the total temporary hearing loss produced by aspirin plus exposure to intense sound was about 10 to 15 dB greater than that produced by exposure to the intense sound alone. A similar effect was observed for sodium salicylate. After similar administrations of sulindac (400 mg per day) and diflunisal (750 mg per day), there was no corresponding increase in the sound-induced hearing loss. Under certain reasonable assumptions about underlying mechanisms, these findings suggest that persons taking moderate doses of aspirin or sodium salicylate may be at increased risk of noise-induced hearing loss.

Adult↗
PubMed1980

Sounds produced by the mandibular joint in young men. A mass examination.

More than 2000 young "healthy" men were asked whether they had noticed sounds emanating from the temporo-mandibular joints when being examined in connection with preventive dentistry. They were examined subsequently. About 20% of the patients said they had noticed occasional sounds emanating from the jaw joints; on palpation, crepitation or clicking was found in more than 10%. Auscultatory examination demonstrated sounds in almost 80% of the individuals examined. Phonographically a smaller group demonstrated sounds in more than 90% of the young men. The evaluation of the symptom "sounds in the joint", important in general practice, is not easy when one considers its frequency in "healthy" individuals.

Adult↗
PubMed2003

Speed of sound in normal and degenerated bovine articular cartilage.

The unknown and variable speed of sound may impair accuracy of the acoustic measurement of cartilage properties. In this study, relationships between the speed of sound and cartilage composition, mechanical properties and degenerative state were studied in bovine knee and ankle cartilage (n = 62). Further, the effect of speed variation on the determination of cartilage thickness and stiffness with ultrasound (US) indentation was numerically simulated. The speed of sound was significantly (n = 32, p < 0.05) dependent on the cartilage water content (r = -0.800), uronic acid content (per wet weight, r = 0.886) and hydroxyproline content (per wet weight, r = 0.887, n = 28), Young's modulus at equilibrium (r = 0.740), dynamic modulus (r = 0.905), and degenerative state (i.e., Mankin score) (r = -0.727). In addition to cartilage composition, mechanical and acoustic properties varied significantly between different anatomical locations. In US indentation, cartilage is indented with a US transducer. Deformation and thickness of tissue are calculated using a predefined speed of sound and used in determination of dynamic modulus. Based on the simulations, use of the mean speed of sound of 1627 m/s (whole material) induced a maximum error of 7.8% on cartilage thickness and of 6.2% on cartilage dynamic modulus, as determined with the US indentation technique (indenter diameter 3 mm). We believe that these errors are acceptable in clinical US indentation measurements.

Animals↗
PubMed2003

Tracking of multiple sound sources defined by interaural time differences: brain potential evidence in humans.

Among other cues, interaural time differences (ITD) can be used to compute the location of a sound. To investigate whether ITD can be used for the preattentive detection of sounds coming from a different location than standard sounds (P=0.7, no ITD), left and right 'far' (900 micros ITD, 80 degrees excentricity) and 'near ' (300 micros ITD, 30 degrees ) deviant stimuli (each deviant P=0.075) were presented via headphones. While 15 young healthy subjects passively listened to these sequences, the mismatch negativity (MMN) of the event-related potential was obtained for the deviant sounds. MMN was reliable for all four deviants but larger for the far-lateralized sounds. Moreover, MMN was larger contralateral to the location of the deviant. This indicates a role of preattentive mechanisms in the spatial analysis of auditory scenes.

Adult↗